Improving the prediction of “rissagues” in the Balearic Islands

The Balearic Islands Coastal Observing and Forecasting System (SOCIB) has implemented a significant improvement in the Balearic RIssaga Forecasting System (BRIFS), developed by SOCIB in close collaboration with key scientific partners and stakeholders in the Balearic Islands such as the Mediterranean Institute for Advanced Studies, IMEDEA (CSIC-UIB), the University of the Balearic Islands (UIB), the Spanish State Meteorological Agency (AEMET) and the Balearic Islands Harbours (PortsIB). This forecasting system aims at complementing the AEMET “Rissaga” alert system by providing quantitative predictions of extreme sea level oscillations associated with meteotsunamis (locally referred to as “rissagues”) in Ciutadella harbour (Menorca, Spain). Meteotsunamis are oceanic long waves with tsunami-like characteristics but of meteorological origin.

Using realistic high-resolution nested atmosphere-ocean models, BRIFS simulations provide 48-hour predictions of air pressure disturbances and associated sea-level response over the Balearic shelf and in Ciutadella harbour. As an improvement of the system, BRIFS is now run twice a day (starting at 00:00 and 12:00 UTC) when high-frequency atmospheric pressure oscillations are detected in the atmospheric model, providing a new opportunity to evaluate the sensitivity of the results to the initial state and forecast horizon. In addition to the sea level and atmospheric pressure time series at different control points of the system, a complementary figure now presents BRIFS forecasts by displaying the “rissaga” warning levels of all available BRIFS simulations for each 6-hour time slot.

Through this computationally affordable approach, the system displays results of a small ensemble of simulations providing a first estimate of the uncertainty associated with the deterministic predictions. This is in line with the recent article published in the journal Natural Hazards, which evaluated the potential of BRIFS ensemble forecasting, showing that small modifications in the numerical approach were leading to significant changes in the details of the small-scale atmospheric structures which in turn impacted the predicted magnitude of the “rissagues”.

Reference article

Mourre, B., Santana, A., Buils, A., Gautreau, L., Ličer, M., Jansà, A., Casas, B., Amengual, B., & Tintoré, J. (2021). On the potential of ensemble forecasting for the prediction of meteotsunamis in the Balearic Islands: sensitivity to atmospheric model parameterizations. Natural Hazards, 106(2), 1315-1336.